w the audacity of the
Dogmatics in a variety of ways.[6] The order of these Tropes is
the same with Diogenes as with Sextus, but the definitions of
them differ sufficiently to show that the two authors took their
material from different sources. According to the first one
everything in question is either sensible or intellectual, and
in attempting to judge it either in life, practically, or "among
philosophers," a position is developed from which it is
impossible to reach a conclusion.[7] According to the second,
every proof requires another proof, and so on to infinity, and
there is no standpoint from which to begin the reasoning.[8]
According to the third, all perceptions are relative, as the
object is colored by the condition of the judge, and the
influence of other things around it.[9] According to the fourth,
it is impossible to escape from the _regressus in infinitum_ by
making a hypothesis the starting point, as the Dogmatics attempt
to do.[10] And the fifth, or the _circulus in probando_, arises
when that which should be the proof needs to be sustained by the
thing to be proved.

[1] _Hyp._ I. 164.

[2] Diog. IX. 11, 88.

[3] Diog. IX. 11, 106.

[4] Diog. IX. 12, 115-116.

[5] Compare Natorp. _Op. cit._ p. 302.

[6] _Hyp._ I. 177.

[7] _Hyp._ I. 165.

[8] _Hyp._ I. 166.

[9] _Hyp._ I. 167.

[10] _Hyp._ I. 168.

Sextus claims that all things can be included in these Tropes,
whether sensible or intellectual.[1] For whether, as some say,
only the things of sense are true, or as others claim, only
those of the understanding, or as still others contend, some
things both of sense and understanding are true, a discord must
arise that is impossible to be judged, for it cannot be judged
by the sensible, nor by the intellectual, for the things of the
intellect themselves require a proof; accordingly, the result of
all reasoning must be either hypothetical, or fall into the
_regressus in infinitum_ or the _circulus in probando_.[2] The
reference above to some who say that only the things of sense
are true, is to Epicurus and Protagoras; to some that only the
things of thought are true, to Democritus and Plato; and to
those that claimed some of both to be true, to the Stoics and
the Peripatetics.[3] The three new Tropes added by Agrippa have
nothing to do with sense-perception, but bear entirely upon the
possibility of reasoning, as demanded by the science of logic,